Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
  • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/28—Treatment of water, waste water, or sewage by sorption
  • C02F1/286—Treatment of water, waste water, or sewage by sorption using natural organic sorbents or derivatives thereof

Definitions

• This invention relates to a process for producing a novel reduced keratinous substance, and more specifically to a novel process for producing a reduced keratinous substance having a high degree of adsorptive power for cationic substances by reducing a substance containing keratin as a main ingredient, such as animal hair fibers (e.g., wool, mohair, cashmere, or camel hair), feathers, hair on the head, horns, hoofs, nails, or the like.
• animal hair fibers e.g., wool, mohair, cashmere, or camel hair
• keratinous substance denotes a substance containing as a main ingredient keratin which is a kind of structural protein.
• Various keratinous substances exemplified above have been known to have a certain degree of adsorptive power for heavy metal ions, especially a mercury ion, and attempts have been made to exploit them as an adsorbent. These keratinous substances alone, however, do not have enough adsorptive capacities and absorbing speeds to meet practical needs, and it is desired to modify them.
• a method has also been known which comprises causing a protein-hydrolyzing enzyme such as papain to act on wool fibers to cleave the polypeptide molecules which constitute the main chain of keratin contained as a main ingredient in the wool fibers, and thereby to form the wool fibers into a flaky fine powder.
• the flaky fine powder of wool fibers is known to be usable, for example, as a fixed layer for chromatography to develop various metal ions. Since, however, the disulfide linkages of keratin still remain, the adsorptive power of the fine powder for various metal ions is much the same as that of the untreated wool fibers. Furthermore, the resulting fine powder has an apparent density of as low as 0.1 to 0.2. The method further has the defect that the enzyme used is expensive, and the yield of the flaky fine powder is low.
• Another object of this invention is to provide a reduced keratinous substance having a high degree of adsorptive power not only for cationic substances, especially a mercury ion, but also for certain anions; and a process for producing the reduced keratinous substance.
• Still another object of this invention is to provide a process for producing easily in a high yield a powdery, granular or flaky reduced keratinous substance having a high degree of adsorptive power for heavy metal ions, especially a mercury ion, and a relatively high apparent density.
• a further object of this invention is to provide a treating agent for industrial waste waters which can remove various heavy metal ions from the industrial wastes by efficient adsorption, and from which the adsorbed heavy metal ions can be recovered easily.
• a process for producing a reduced keratinous substance having a high adsorptive power for cationic substances which comprises reducing a substance containing keratin as a main ingredient under alkaline conditions to cleave the disulfide linkages of the keratin, dissolving the reduced keratin in an aqueous medium containing urea or thiourea in a concentration of less than 5 moles/liter, and then acidifying the resulting solution to precipitate the dissolved reduced keratin under such conditions that the thiol side-chains present in the reduced keratin do not substantially undergo oxidation.
• a naturally occurring substance containing keratin as a main ingredient is used as a starting material, and reduced under alkaline conditions to cleave substantially completely the disulfide linkages (--S--S--) which form intermolecular bridging chains for the polypeptide chains constituting the keratin;
• the reduced keratin is substantially dissolved in an aqueous medium containing urea or thiourea in a relatively low concentration of less than 5 moles/liter;
• the reduced keratinous substance provided by the present invention is generally a pale gray to pale yellow, non-transparent, powdery to flaky solid particulate substance, although these characteristics differ according to the type of the starting keratinous substance.
• the reduced keratinous substance generally has an average particle diameter of 0.02 to 20 mm, preferably 0.2 to 2 mm, and an apparent density, which varies depending upon the dried condition, of generally 0.1 to 1.0 g/cm 3 , and usually 0.3 to 0.5 g/cm 3 , which apparent density is far higher than those of the conventional modified keratinous substances.
• the reduced keratinous substance of this invention may have a surface area of generally 0.1 m 2 /g to 200 m 2 /g, usually 10 m 2 /g to 100 m 2 /g.
• the disulfide linkages which form bridging chains for the polypeptide chains of keratin are cleaved by reduction, while substantially retaining the resulting thiol (--SH) side-chains, the reduced keratinous substance is precipitated by utilizing a difference in solubility (isoelectric point).
• the reduced keratinous substance provided by this invention contains a very large amount of thiol groups (--SH).
• the reduced keratinous particles of the invention are very reactive, and have a high degree of selective adsorptive power for various cationic substances, especially a mercury ion.
• Keratin is a kind of structural (tissue) protein present in large amounts in the skin of vertebrate animals and their tissues growing outwardly of the skin. It is present in great amounts in various tissues of vertebrate animals such as hair, feathers, horns, hoofs and nails. Accordingly, any materials which contain true keratin as a structural protein can be used as a starting material. Examples of the starting material are therefore the horns, hoofs, nails, feathers, and hairs of vertebrate animals; and preferred materials are wool and feathers. These materials can be used either as such or after having been pulverized or cut to suitable sizes.
• the keratinous substances as starting materials may be pre-treated, for example by washing or defatting.
• the polypeptide chains of the keratinous substances are three-dimensionally crosslinked by, for example, disulfide linkages (cystein bridging), salt-forming crosslinking (bridge) or hydrogen bonding, the keratinous substances are insoluble or only slightly soluble in ordinary solvents, and are not sufficiently decomposed by ordinary proteinases. It is not easy therefore to make them directly into the form of powder, flake, granule, or the like.
• such a keratinous substance is reduced under alkaline conditions to cleave the disulfide linkages present in the keratin.
• the reduction is performed generally in an aqueous medium.
• Any aqueous media which are stable to reduction and preferably have an affinity for the starting keratinous substance can be used in this invention.
• the aqueous medium is water itself or a mixture of it with a water-miscible organic solvent.
• the water-miscible organic solvents are lower alkanols such as methanol, ethanol or propanol, phenols such as phenol or cresol, amides such as formamide, and dimethyl sulfoxide.
• solvents can be used either alone or as a mixture of two or more.
• lower alkanols especially isopropanol
• the ratio between water and the organic solvent is not particularly limited, and can be varied over a wide range according, for example, to the type of the starting keratinous substance and the type of the reducing agent.
• water is desirably contained in an amount at least equal to the volume of the organic solvent.
• the suitable ratio of water to isopropanol is 75:25, especially 80:20.
• the starting keratinous substance is dipped in the aqueous medium.
• the weight ratio of the keratinous substance to the aqueous medium there is no strict limitation on the weight ratio of the keratinous substance to the aqueous medium.
• the ratio of the keratinous substance to the aqueous medium is conveniently 1:at least 5, usually 1:10 to 1:100, preferably 1:20 to 1:50.
• Any reducing agent can be used which can cleave the disulfide bonds (--S-S--) in the keratinous substance to thiol groups (-SH).
• organic and inorganic reducing agents which act nucleophilically on disulfide bonds (--S-S--) are preferred.
• Suitable organic reducing agents are thiol derivatives and phosphorus-containing compounds.
• Example of organic reducing agents that can be used advantageously are mercaptoethanol, thioglycolic acid and its esters, tributyl phosphine, triphenyl phosphine, and tributyl phosphite.
• suitable inorganic reducing agents are sulfites such as sodium sulfite; potassium sulfite and ammonium sulfite; hydrogen sulfites such as a sodium hydrogen sulfite and potassium hydrogen sulfite; hydrosulfides such as sodium hydrosulfide, potassium hydrosulfide and ammonium hydrosulfide; and sulfides such as hydrogen sulfide, sodium sulfide, potassium sulfide and ammonium sulfide.
• the reduction can be performed by any known methods.
• the thiol derivative or inorganic reducing agent when used, it is used preferably in an excessive equivalent weight, usually at least two equivalent weights, preferably 4 to 10 equivalent weights, per disulfide bond in the keratinous substance.
• the sufficient amount of the phosphorus-containing compound used as a reducing agent is generally equivalent to or somewhat in excess of the amount of the disulfide bonds in the keratinous substance.
• the amount of the disulfide linkages in the keratinous substance can be determined by a colorimetric method, polarography, or amino acid analysis, and specific procedures used in these methods are known [M. Friedman, A. T. Noma, Textile Res. J., 40, 1073 (1970); Hideaki Munakata, Yoshiharu Niinami, Journal of Japanese Textile Society, 19, 392 (1963); Ryoji Nakamura and Yoshio Nemoto, Journal of Japanese Textile Society, 17 428 (1961)].
• the reduction in accordance with this invention is carried out advantageously under alkaline conditions to aid in the swelling of the keratinous substance, and to perform the reduction as fully, uniformly and rapidly as possible.
• the alkalinity attained at this time is expressed by a pH of at least 7.5, preferably about 8 to about 11, more preferably 10 to 11.
• Adjustment of the pH can be made by adding an inorganic or organic alkaline substance to the reaction system.
• alkaline substances that can be used include inorganic alkalies such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, and organic bases such as trimethylamine, triethylamine, guanidine, 1,5-diazo-bicyclo(4,3,0)-nonene-5, and 1,8-diazo-bicyclo (5,4,0)-undecene-7.
• Such an alkaline substance is added so as to maintain the pH within the above specified range.
• the temperature and pressure used at the time of the reduction there is no particular restriction on the temperature and pressure used at the time of the reduction, and these conditions can be varied according, for example, to the type of the reducing agent used or the type of the starting keratinous substance.
• Room temperature is sufficient for performing the reduction.
• the reduction may be carried out under heat, for example at a temperature of up to about 90° C.
• Atmospheric pressure is sufficient as the reaction pressure, but if desired, the reducing reaction can be performed under reduced or elevated pressures.
• the reduction is performed in an inert gas atmosphere, for example, in an atmosphere of nigrogen or carbon dioxide gas.
• the reduction described hereinabove results in the cleavage of the disulfide linkages in the keratinous substance, and the keratinous substance becomes substantially soluble in the aqueous medium.
• Some types of keratinous substance do not dissolve sufficiently in the aqueous medium even after the cleavage of the disulfide linkages in the keratinous substances, because secondary bonding (i.e., hydrogen bonding, salt-forming bonding, and hydrophobic bonding) occurs owing to the association of the carboxyl groups, amino groups, hydroxyl groups and other hydrophobic groups (e.g., methyl or dimethyl groups).
• urea or thiourea especially the former, which are frequently used in the field of protein chemistry as a "disassociating agent" having the property of destroying the secondary bonding is included in the aqueous media.
• the concentration of urea or thiourea to be included in the aqueous medium is very important for the precipitation of the reduced keratinous substance. It is critical to limit this concentration to less than 5 moles/liter, especially not more than 4.5 moles/liter. The lower limit to this concentration may be 1 mole/liter.
• the concentration of urea or thiourea in the aqueous medium is preferably 1 to 4 moles/liter, more preferably 2 to 4 moles/liter.
• the reduced keratinous substance can therefore be substantially dissolved in the aqueous medium. Dissolving can be promoted by elevating the temperature of the mixture.
• a water-soluble inorganic salt such as sodium iodide, lithium bromide or lithium iodide can be added as a dissolution aid.
• a water-soluble inorganic salt can be added in an amount of generally at least 1 mole/liter, preferably 2 to 5 moles/liter, more preferably 3 to 4 moles/liter.
• urea or thiourea and the water-soluble inorganic salt to the aqueous medium is not critical. They may be dissolved beforehand in the aqueous medium, or may be added to the reaction mixture obtained by reduction. Generally, it is advantageous to dissolve urea or thiourea in the aqueous medium in the aforesaid concentration before the performance of the reducing reaction.
• suitable media for the reducing reaction are a water-urea-sodium hydroxide solution and a water-urea-ammonia solution both having a pH of 8 to 11.
• the reduced keratinous substance can be dissolved substantially in the aqueous medium containing urea or thiourea in the above-specified concentration.
• its concentration in the aqueous medium should not be too low.
• the concentration of the reduced keratin is generally at least 0.5 part by weight, preferably 1 to 10 parts by weight, and more preferably 2 to 5 parts by weight, per 100 parts by weight of the aqueous medium.
• the resulting solution in which the keratin whose disulfide linkages have been cleaved by reduction is dissolved substantially is then submitted to the subsequent acidifying step. If the solution contains insoluble foreign substances and insoluble solids such as cellular membranous substances which have been introduced together with the starting keratinous substance, they should be separated by such means as filtration or centrifugal separation before the acidification step.
• the separating operation is preferably carried out in an atmosphere of an inert gas.
• the reduced keratin can be precipitated as a solid by acidifying the solution containing the reduced keratinous substance. It has been found in accordance with this invention that when the pH of the solution of the reduced keratin dissolved under alkaline conditions in the aqueous medium containing urea or thiourea in a concentration of less than 5 moles/liter is shifted to an acidic side, the solubility of the reduced keratin decreases markedly and the keratin precipitates as a gel. The decrease of the solubility is believed to be a reduction in solubility by isoelectric point, and the revival of the secondary bonding by the insufficient amount of urea or thiourea.
• the pH of the solution required for precipitation is not critical.
• the pH may be more than 6 at which the solution is slightly acidic. It is generally preferred however to adjust the pH of the solution to not more than 6 because at a higher pH, the reduced keratin tends to be precipitated as a colloid or ultrafine suspended gel, and the thiol groups in the reduced keratin are not stabilized.
• the lower limit to the pH value is neither critical, and strongly acidic pH values can also be used. Since too strong an acidity may cause hydrolysis of the peptide bonds in the reduced keratin, the pH of the solution is usually about 4 to about 6, preferably 4.5 to 5.5.
• the adjustment of the pH can be easily performed by adding to the solution of the reduced keratin a water-soluble acidic substance, for example an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or an organic acid such as acetic acid, propionic acid, or p-toluenesulfonic acid.
• a water-soluble acidic substance for example an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, or an organic acid such as acetic acid, propionic acid, or p-toluenesulfonic acid.
• an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid
• an organic acid such as acetic acid, propionic acid, or p-toluenesulfonic acid.
• Use of volatile acids especially hydrochloric acid is preferred because, for example, of the ease of separating the acid from the resulting
• the precipitating operation by acidification should be performed under such conditions that the thiol groups in the reduced keratin do not undergo substantial oxidation.
• it is desirable to perform the precipitating operation under non-oxidizing conditions for example, in an atmosphere of an inert gas such as nitrogen or carbon dioxide gas.
• the precipitating operation may also be performed in the air if it is done under such conditions that the reduced keratin is not substantially oxidized, for example under such conditions that the air contacts only the surface of the solution containing reduced keratin, and is not blown into the solution.
• Room temperature is usually sufficient as the temperature for the precipitating operation. But if desired, gellation may be promoted by cooling the solution. Reduced keratin gels having a more uniform particle size can be obtained by gradually adding the acid with stirring rather then by adding the acid abruptly at a time.
• Size adjustment of the solid particles of the reduced keratin substance can be easily performed by properly selecting the concentration of the reduced keratin in the solution, the degree of acidification of the solution, the temperature, the stirring conditions, etc.
• the reduced keratinous substance formed as a powder granule or flake can be recovered by ordinary methods such as filtration or centrifugal separation.
• the solid particles of the reduced keratinous substance can be dried by ordinary means. It is necessary at this time to select temperatures and atmospheres which do not cause the substantial oxidation of the reduced keratinous substance.
• the solid particles are dried in an atmosphere of an inert gas at a temperature of usually not more than 80° C., preferably not more than 60° C. Drying under reduced pressure is most preferred, but the drying method is not limited to it. Other drying methods can also be used properly. For example, it is advantageous to replace the aqueous medium accompanying the solid particles of the reduced keratinous substance by an alcohol, especially methanol or ethanol, and then drying the mixture.
• the reduced keratinous substance separated, recovered and dried is generally a pale gray to pale yellow flaky to fine powdery material with the individual particles have an irregular surface with a microporous structure.
• the reduced keratinous substance obtained can be directly used in applications described hereinbelow.
• the reduced keratinous substance produced by the process of this invention exhibits a high degree of selective adsorptive power for cationic substances, for example heavy metal ions, especially a mercury ion and a mercury-containing organic compound such as methyl mercury, and have different adsorptive powers for certain kinds of anionic substances, such as bichromate radical (Cr 2 O 7 -2 ), a thiocyanide ion (CNS -1 ), and silver cyanide [for example, a ferrocyanide radical (Fe(CN) 6 -4 ) or a ferricyanide radical (Fe(CN) 6 -3 )].
• Industrial wastes containing these cationic substances and/or anionic substances in various concentrations can be treated with the reduced keratinous substance of the present invention to separate or remove the cationic and/or anionic substances with good efficiency.
• the reduced keratinous substance of this invention has a very high speed of adsorbing the cathionic substances and/or anionic substances, and has the ability to adsorb these substances very effectively from a solution containing them within very short periods of time.
• the reduced keratinous substance of this invention has the ability to remove substantially all of cationic substances and/or anionic substances from a solution containing them in very low concentrations.
• one gram of the reduced keratinous substances of this invention when treating 100 liters of a waste water containing a mercury ion in a concentration of as low as 1 ppm, can reduced the Hg concentration to 0.0001 ppm or below.
• the reduced keratinous substance of this invention is a polypeptide and can be easily hydrolyzed with a conc. alkali or acid, no special operation such as calcination of the conventional metal adsorbing chelate resins is required, and there is no likelihood of causing secondary pollution.
• the reduced keratinous substance of this invention can be used for the separation, removal or recovery of various cationic substances, especially heavy metal ions, and/or anionic substances from various solutions, especially industrial waste waters, either in the form of a fine powder, granule or flake as obtained, or after having been molded into a suitable shape such as a pellet, film, sheet or plate.
• the reduced keratinous substance provided by this invention can be used especially advantageously as a heavy metal capturing agent.
• the precipitate was filtered in a stream of nitrogen, and washed until most of the urea and mercaptoethanol were removed.
• the washed product was dried under reduced pressure.
• the yield of the reduction product obtained was 75% based on the weight of the starting wool fibers, and it had an apparent density of 0.32 g/cc.
• the product was packed into an adsorption column having an inside diameter of 15 mm and a length of 250 mm, and 10 liters of an aqueous solution containing 50 ppm of a mercury ion was passed through the packed column.
• the mercury concentration of the effluent was measured by an atomic adsorptiometric method. No mercury ion was detected from the effluent.
• the reaction mixture was stirred while adding 6N hydrochloric acid in a stream of nitrogen to adjust the pH to 5, whereupon a flaky pale yellow precipitate formed.
• the precipitate was filtered in a stream of nitrogen, and wahsed until most of the urea and mercaptoethanol were removed.
• the washed product was dried under reduced pressure.
• the yield of the reduction product was 62% based on the starting wool fibers, and the product had an apparent density of 0.38 g/cc.
• the adsorptive power of the reduced keratinous substance was packed into an adsorption column having an inside diameter of 15 mm and a length of 250 mm, and an aqueous solution containing 29.4 ppm of a mercury ion and 7.0 ppm of a copper ion was passed through it.
• the effluent was found to contain 0.0004 ppm of a mercury ion and 0.2 ppm of a copper ion.
• Example 1 The procedure of Example 1 was repeated except that the amount of the wool fibers was changed to 40 g and the amount of the mercaptoethanol was changed to 20 cc.
• the reduction product was finer in size than the product obtained in Example 1, and was easy to wash with water and dehydrate.
• the yield of the reduction product was 80% based on the starting wool fibers, and the product had an apparent density of 0.37.
• Example 2 The procedure of Example 1 was repeated except that defatted feathers of chicken (white Leghorn) were used instead of the wool fibers.
• the reduced feathers had better solubility than wool fibers, and the resulting reaction mixture containing the feathers dissolved in it had an insoluble content of only 2 to 3%.
• the insoluble matter was removed by filtration in a stream of nitrogen.
• 6N hydrochloric acid was added to the filtrate to reduce its pH to 5 and thereby to form a precipitate.
• the yield of the resulting reduced keratinous substance was 66% based on the starting feathers, and the product had an apparent density of 0.28 g/cc.
• the adsorptive power of the reduced keratinous substance was packed into an adsorption column having an inside diameter of 15 mm and a length of 250 mm, and an aqueous solution containing 10 ppm of a mercury ion was passed through it.
• the effluent had a mercury ion concentration of only 0.002 ppm.
• the precipitate was filtered, washed with water and dried in a stream of nitrogen to afford a reduced keratinous substance in a yield of 78% based on the starting wool fibers.
• the apparent density of the product was 0.38 g/cc.
• the adsorptive power of the reduced keratinous substance was packed into an adsorption column having an inside diameter of 15 mm and a length of 150 mm, and the mercury concentration of the effluent was measured by an atomic absorptiometric method. No mercury ion was detected from the effluent.
• the precipitate was filtered, washed with water, and dried under reduced pressure in a stream of nitrogen to afford a reduced keratinous substance in a yield of 78% based on the starting wool fibers.
• the apparent density of the fibers was 0.35 g/cc.
• the adsorptive power of the reduced keratinous substance was packed into an adsorption column having an inside diameter of 15 mm and a length of 250 ml, and 10 liters of an aqueous solution containing 50 ppm of a mercury ion was passed through it.
• the mercury concentration of the effluent was measured by an atomic adsorptiometric method. No mercury ion was detected from the effluent.
• a reduced keratinous substance was obtained in a yield of 81% based on the starting wool fibers, and the product had an apparent density of 0.39 g/cc.
• the resulting reduced keratinous substance had the ability to remove a mercury ion completely.
• the precipitate was filtered in an atmosphere of nitrogen, and washed until most of the urea and reducing agent was removed, followed by drying under reduced pressure.
• a reduced keratinous substance having an apparent density of 0.33 g/cc was obtained in a yield of 80%.
• Example 8 The procedure of Example 8 was repeated except that 20 g of sodium sulfite was used instead of the sodium hydrosulfide, and the pH of the solution for precipitation after the reduction was changed to 4.0. A reduced keratinous substance having an apparent density of 0.32 g/cc was obtained in a yield of 81%.
• the precipitate was filtered in an atmosphere of nitrogen, and washed until most of the urea and reducing agent was removed, followed by drying under reduced pressure. A reduced keratinous substance having an apparent density of 0.37 g/cc was obtained in a yield of 75%.
• the precipitate was filtered in a stream of nitrogen, and washed until most of the urea and reducing agent was removed, followed by drying under reduced pressure.
• a reduced keratinous substance having an apparent density of 0.2 to 0.9 g/cc was obtained in a yield of 76%.
• the average particle diameter, the thiol group content, the Hg adsorbing ability, and the surface area of the reduced keratinous substances obtained in the foregoing Examples were determined. The results are tabulated below together with the yields and apparent densities of the products.
• the thiol group content, the Hg adsorbing ability and the surface area were measured by the following methods.

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• 1977
  • 1977-03-07 JP JP52024999A patent/JPS603104B2/ja not_active Expired
• 1978
  • 1978-03-03 AU AU33809/78A patent/AU522321B2/en not_active Expired
  • 1978-03-06 DE DE2809559A patent/DE2809559C2/de not_active Expired
  • 1978-03-06 US US05/883,997 patent/US4141888A/en not_active Expired - Lifetime
  • 1978-03-07 IT IT20968/78A patent/IT1094180B/it active
  • 1978-03-07 GB GB9061/78A patent/GB1567729A/en not_active Expired
  • 1978-03-07 FR FR7806442A patent/FR2383196A1/fr active Granted

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